In this specification, unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge, or any combination thereof, was at the priority date, publicly available, known to the public, part of common general knowledge, or known to be relevant to an attempt to solve any problem with which this specification is concerned.
There is an ongoing demand for new games and variations of games to maintain player interest. The provision of bonus features provides a method for maintaining player interest.
Reel-type gaming machines have an electronic simulation of a plurality of spinning reels. The individual reels stop in a position relative to a display to show one or more rows of symbols from adjacent reels in a window or in a virtual display and a matrix of rows and columns of symbols is displayed for analysis of winning or losing events. A common window configuration is three rows and five columns, but other combinations are also known. One or more paylines are defined in the window, for example, the centre row, the top row, the bottom row, and possibly one or more meander lines. Non-linear paylines and “scatter” pays are also known. The player may select (by wagering) one or more paylines per game. The paylines are normally selected in a fixed sequence; for example, if the player selects one payline, this will normally be the central horizontal line. Similarly, selecting two paylines will activate the centre payline and the top horizontal payline. The player may also select the amount wagered per line. A payline is active if the player has wagered sufficient paylines to include that payline or specifically selected individual paylines or groups of paylines. Paylines which are not active are inactive.
In a standard video format of such games on electronic gaming machines (hereinafter defined as “EGM” or “EGMs”), the virtual reels are made to appear to spin, each virtual symbol being made to appear to traverse its column in the window in a fixed sequence in relation to its adjacent symbols. When the virtual reels cease to spin, the virtual symbols displayed in the window on each active payline are compared with a paytable to determine if a prize has been won.
Bonus awards can be triggered when a bonus trigger symbol or bonus trigger event (e.g., specific multiple symbols or a random bonus event) is displayed in the window. The game has rules or algorithms or programs for determining the probability of a bonus trigger symbol being included on a reel.
In known systems, when it is desired to add a bonus trigger symbol to a reel, an additional symbol is added to the reel, virtual reel or into software providing virtual images. Thus, for a reel having L symbols in a standard game (physical reel or virtual reel), the reel with the bonus trigger symbol will have L+1 symbols. This, of course, alters the probabilities of the game. Accordingly, it is necessary to revise the payouts and odds with respect to the new probabilities to achieve the intended payout ratio or percentages.
Electronic gaming machines are capable of implementing different games on the same machine. Some of these games can have differing numbers of symbols on their reels. The inclusion of additional bonus trigger symbols in such machines may require the recalculation of probabilities for each different game.
Some slot machines include bonus features that are activated randomly or pseudo-randomly and the bonus features are normally independent of the results of the underlying or primary game. The result of the primary slot game is determined by the resulting symbols on the reels and the paylines being wagered on by the player, whereas bonus features are generally triggered independently of the result of the primary game. In some cases, the bonus features are triggered randomly by the EGM with no visual indicator shown, unless the bonus feature is actually triggered by specific visual or displayed events. In other cases, the bonus feature is triggered by the appearance of a bonus symbol in one of the active and, sometimes, the inactive paylines. This is called a symbol-driven method of triggering a feature, and the bonus symbols, or some other indicia, are added to the reel strip or strips or are identified by software as being part of a bonus triggering event. For example, in video poker games, the conventional symbols forming four-of-a-kind or a straight flush may be used to trigger a bonus event without having to add any additional symbols.
If the bonus feature is triggered by a symbol that is part of the reel strip (i.e., the bonus feature symbol occupies one of the positions on the reel strip), then the probability of the bonus or triggering symbol appearing (known as the feature hit rate) is based on the length of the reel (or total number of symbols in a virtual reel) and the number of triggering symbols that appear on the reel.
Any attempt to add common bonus features to a plurality of different games presents difficulties because different games have different reel lengths, different numbers of virtual symbols per different reels, and different probabilities for different symbols in virtual reels for different games, and to keep the hit rate of the bonus feature approximately constant would require that the game mathematics be modified for every different game. This adds additional expense and development time to game design and is therefore undesirable.
Therefore it is desirable to have a bonus feature and a method of triggering a bonus feature that operates independently of the underlying game and its particular features and mathematics.
U.S. Publication No. 2007/077986, now U.S. Pat. No. 7,585,220, issued Sep. 8, 2009, discloses a spinning reel slot machine comprising a plurality of mechanical rotatable reels and a video display. In response to a wager, the reels are rotated and stopped to randomly place symbols on the reels in visual association with a display area. The video display provides a video image superimposed upon the reels. The video image may be interactive with the reels and include such graphics as payout values, a paytable, paylines, bonus game features, special effects, thematic scenery, and instructional information.
U.S. Publication No. 2005/0159208, now U.S. Pat. No. 7,654,895, issued Feb. 2, 2010, discloses a slot-type gaming machine using an expandable symbol array to create a series of sequentially larger symbol arrays with the potential for additional or enhanced awards. The generation of the larger arrays can be performed through a variety a different mechanisms, such as the addition of a reel to the base array. The secondary arrays may be generated only under specific sets of circumstances that occur in the base array, including a winning payline, the occurrence of a bonus triggering symbol, etc. To increase player interest in the game, some embodiments include allowing the player to determine where the additional symbols to create the larger array are placed in the base array.
EP1544811 discloses a gaming machine having an enhanced game play scheme where, in response to receipt of a second wager to select an option, a player is provided with enhanced game play that may include, among other features, providing an extra wild symbol capable of repositioning.
U.S. Pat. No. 5,980,384 to Barrie discloses a gaming apparatus and method in which there is a primary game and a secondary game that are dynamically linked, and the primary game can be won independently of the secondary game. The primary game may be won on each play of the game, and the secondary game may be won over a plurality of plays of the primary game. Primary game symbols appearing during plays of the primary game may cause: (i) movement of primary game symbols to secondary game display positions; (ii) primary game symbols directing play options of secondary game symbols; (iii) changing the options open to the player in his or her attempt to win the secondary game; (iv) symbols in the primary game being used as soft buttons to affect movement of game symbols from the primary game to the secondary game, and between symbol display positions in the secondary game; and (v) secondary game symbols persisting to subsequent plays of the primary game to help the player to win at the secondary game.
It is desirable to provide an electronic gaming machine with the ability to incorporate bonus trigger symbols without affecting the standard game probabilities.